Method and apparatus for rectifying high-tension alternating current



Feb,20,1923. 1,445,988. =G,A .wnTE.

METHOD AND APPARATUS FOR RETIFYING H iGH TENS|0N\ALT ERNATING CURRENT.

, FILED APRQa. 1919.

50 ,3 -34 4 3 a P 2 15 35 I 3 W INVENTOR I Cum P 4W ATTORNEY PatentedFeb. 20, 1923.

UNITED STATES I PATENT OFFICE.

GUSTAV A. WITTE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO INTERNA-TIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORA-TION OF CALIFORNIA.

METHOD AND APPARATUS FOR RECTIFYING HIGH-TENSION ALTERNA'IING CURRENT.

Application filed April 8, 1919. Serial No. 288,652.

To all whom it nlay concern: 7

' Be it known that I, GUSTAV A. urn, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented a new'and useful Method and Apparatus forRectifying High-Tension Alternating Cur-- rent, of which the followingis a specification.

This invention relates to the rectification of high tension alternatingcurrent by means of a mechanical rectifier that is to say, a mechanicaldevice operated in synchronism with the alternating current and-actingto make and break connection between the supply circuit and a load ortranslating device, in such manner that only unidirectional impulseswill be transmitted to the latter. In apparatus of this character, theconnection established thereby generally includes air gaps between theshoes or stationary conductors and moving conductors thereof, and

there is, in general, a tendency to sparking between such stationary andmoving conductors, especially at the moment of break or interruption ofcircuit, this resulting not only in objectionable wear on the shoes orconductors, but also in objectionable current phenomena in the loadcircuit. This is particularly the case where the load supplied throughthe rectifier is one presenting high capacity and considerableconductance, such as a treater for precipitating suspended material fromgases by electrical action. In such case, the sudden fluctuations orsurges produced in the load circuit upon occurrence of sparking at therectifier shoes or contacts. interfere seriously with the efliciency ofthe precipitating opeaation. The main object of the present invention isto wholly or largely eliminate such sparking at the rectifier shoes orcontacts. This object attain by applying to the shoes or contacts at oradjacent to the point of interruption of t-he current finely dividedsolid material in the form, for example, of dust.

The accompanying drawings illustrate embodiments of my invention, andreferring thereto:

Fig. 1 is a vertical section of one form of apparatus suitable forcarrying out my invention;

Fig. 2 is'a section on line 2-2 in Fig. 1;

Fig. 3 is a vertical section of another form of the invention. 1

Referring to Fig. 1. the rectifier therein shown comprises a shaft 1mounted on suitable bearings to rotate within a. box orcasing 2; aninsulating disc 3 carried by said shaft, metallic segments 4 and): onsaid disc'and stationary shoes 5?, 5 5 and 5 mounted in fixed positionadjacent to the periphery of said disc. The respective shoes aforesaidare shown as arranged 90 apart and the metallic segments 4 and 4* on therectifier disc 3 are about 90 long so that. said segments will establishconnection successively between adjacent pairs of shoes in well knownmanner. Opposite shoes 5 and 5 are mounted on insulators 6 and are 0011-nected by wires 7 and 8 to opposite ends of" the high tension coil 9 ofa step-up transformer whose low tension coil 10 is connected toalternating current supply circuit wires 11 and. 12. Said wires 7 and 8areinsulated in any suitable manner, to provide for high potentialdifference, say 50,000 volts or more, between the same. A conductor. 14is connected to shoe 5 mounted on an insulator 6 and is connected to awire 16 leading to the load to be supplied from the rectifier. Shoe 5 isgrounded by a connection 19. Suitable insulators 13 are provided forWires 7 8 and 14 where they pass through the walls of easing 2. Shaft 1is rotated in synchronism with the alternating current to be rectified,for exampla'by means of a synchronous motor '15 connected by wires 17and 18 to the alternating current supply circuit 11 and 12, or, as iswell known in this art, said shaft may be direct driven from a motorgenerator set, which serves to produce the high tension alternatingcurrent on the wires 7 and 8 in well known manner, and as set forthiii-patent to F.- G. ottrell. No. 895,729, dated August 11.. 1908.Insulators 6 for shoes 5", et cetera, are shown as bars carried by aframe 24 mounted in bearings 25 and 25 and adapted for angularadjustment by suitable means indicated at 26, to synchronize theoperationv of the apparatus with the alternating current supply circuit.Stuffing boxes 27 may be provided where the bearings 25 and 25 passthrough the wall f? (will of casing 2 and a stufiing'box 27 where shaft1 passes through bearing 25 My invention comprises means .for supplyingdust or other vapor producing means to the breaks orgaps between theshoes and rotating conductors of the rectifier. For this mr ose I ma asshown in Fi 1 rovide means for supplying dust to the interior of easing2, such means consisting, for example, of an air blast pipe connected toa suitable source of compressed air and provided with means, indicatedat 21, for feeding dust thereinto, and with a valve 20 for regula-' tingthe supply of air, or a manhole or door 22 may be. provided forintroducing the dust. In order to protect the bearings of shaft 1 fromgrit present in the dust, said bearings are preferably outside of thecasing 1, as

' shown in F i g. 2, wherein one end of the shaft is mounted in abearing 23 and the other end of the shaft is connected to or constitutesan extension of the shaft of the driving motor or generator 15.

In the operation of the rectifier the dust present in the chamber 2 andsupplied thereto by the air blast means 20, or, ifdesired, through door22, is stirred up or agitated by the windage of the rectifier, aided bythe air blast, so that the atmposhere in which the rectifier rot-ates ischarged with dust and suflicient dust is present between the stationaryshoes and rotary conductor members to alreason of such lowering ofresistance the current is decreased more slowly and gradually oninterruption thereof than would otherwise be the case. This gives a moregradual and less violent break and a smoother and more efiicientlyoperating current supply on the load circuit.

If the casing 2 is sufficiently charged with dust the windage of therectifier itself may be sufficient to maintain the circulation of thedust therein without requiring'the air blast or agitating meansaforesaid.

The invention may also be carried out by direct supply of the dust tothe rectifier, for example, as shown in Fig. 2, wherein a dustfeedingmeans is mounted in position to drip or sprinkle dust onto the rotatingmember ofthe rectifier. rSaid feeding means com prising, for example, apan 30 pivoted at 31 and agitated or vibrated by rotating tappet'means'32, said pan being directly below a dust feed pipe 33 so as toreceive dust from the pipe and discharge it into the rotary rectifiermember 3, the windage of such rectifier member carrying the round to theseveral sets of contact. The re, .fer prothis invention has been justsuch as is obtainable from electrical precipitating apparatus used incollecting the dust and fume from cement kilns. Such dust contains aconsiderable proportion o't volatile alkaline material and it is assumedthat the beneficial efl ect of this dust presented at the point ofcurrent disruption is due largely to the presence of vapors of suchalkaline material produced from the dust by the heat the electric sparkspassing therethrough or the heatof the discharge between the shoes andthe moveable contacts of the rectifier, and my invention includes anyequivalent means for producing vapors at or adjacent to such shoes orcontacts. Heated vapors of alkalies or metals are generally moreconducting than the air or other dielectric in which the currentdisruption takes place, and the effect of the presence of such vapors istherefore to produce a zone of comparatively conducting vapor betweenthe shoes and movable conductors of the rectifier in such manner thatthe interruption of current takes place gradually, as the comparativelyconducting vapor affords a path of gradually increasing resistance for.the current between the moving conductors :and the stationary shoes,which can be drawn out to a considerable extent before the resistancethereof becomes so high as to actually break the connection.

Another advantage of this invention is that the relatively highconductivity of the vapor Zone interposed between the shoes and themoveable conducting members re- .05 duces the effective resistance oftherectifier as a whole as compared with the ordinary air' gap rectifiersnow in use wherein the drop of voltage at the rectifier, due toresistance of the air gap between the shoes and 1m rotating conductingmembers of the rectifier, decreases appreciably the potential differenceactually applied to the load.

The characteristic feature of the invention in its broadest aspect isthe applica- 6 tion of a substance which directly or indirectlyincreases the conductivity of the dielectric at the point ofinterruption. Solid material to be applicable must necessarily be in astate of fine subdivision. In the claims ruption.

'cent. to but out of contact with -ber provided with means for operationthereof in synchronism with I the alternating current and withconductors rotating adjasaid stationary conductors to interrupt theconnection a from the supply current to the load circuit through airgaps betweenthe rotary and stationary conductors, and means for supplying finely divided solid material to said air gaps. I

4. An apparatus according to claim 3 wherein the rectifier is enclosedin a casing provided with means for supplying dust L thereto and foragitating the air within the casing to keep said dust in suspension;

In testimony whereof I have hereunto subscribed my name this 31 day ofMarch GUSTAV A. WITTE.

